Centralized traffic controlling system for railroads



T. J. JUDGE mm. m, 1936.

CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS Filed Sept. 22,1932 W Emu TINUV 5 55m w lmml wumwm E w ATTORNEY Patented Oct. 27, 1936UNITED STATES CENTRALIZED TRAFFIG CONTROLLING SYSTEIVLFOR RAILROADSThomas J. Judge, Rochester, N. Y., assignor to General Railway SignalCompany, Rochester,

Application September 22, 1932, Serial No. 634,374

20 Claims.

This invention relates to railway centralized traffic controllingsystems and more particularly to a system of the non-coded or directcontrol type, as distinguished from a station selecting type of system.

It is proposed in accordance with the present invention to provide ameans for controlling a remote power operated track switch by thepolarity of energy applied at the control point to one line circuit, andto control the traffic as well as the direction of trafiic over thisswitch by selectively applying either of two polarities of energy to asecond line circuit. It is also proposed to provide means for indicatingover these same two line circuits the response of the track switch tothe transmitted control therefor, a clear signal and the particulardirection which such a signal governs, and the presence of a train on aparticular track section. It is further proposed to provide suchinterlocking of circuits in the communication of controls andindications which will prevent the transmission of conflicting controlsand yet which will retain sufficient operating flexibility for theefficient direction of traffic movements.

Other objects, purposes and characteristic features of the inventionwill appear as the description thereof progresses, in which, referencewill be made to the accompanying drawing which illustrates in adiagrammatic and conventional manner one specific embodiment of thepresent invention which is susceptible of considerable modification oradaptation in practice depending on the type of controls required andthe character and number of indications which are consideredadvantageous in the particular application.

In the accompanying drawing, a complete communicating system is shownfor transmitting controls and indications between a typical outlyingfield station and apparatus associated therewith at a control office. Itis to be understood, however, that in a practical application of thissystem, there will be considerable distance between a field station andthe control office, and it is necessary to extend only three line wiresover this distance, namely, wires L L and the wire COM, which wire COMmay, if desired, be the common wire for the complete centralized trafficcontrolling system. In systems having several outlying field stationstwo line wires such as L and L will of course be required for each suchstation. The field station apparatus as well as the control ofiiceapparatus, as designated by the legends on the drawing, will also beduplicated for each of the outlying field stations.

A portion of a track diagram which is associated with the typicalsection of track to which this invention is applied is diagrammaticallyshown in the accompanying drawing with an indicating light OSI of theconventional type arranged to display an indication of the presence of atrain upon a particular section of track and similar indicating lightsESK, WSK, and WSAK, are shown to simulate the actual light signals whichgovern traffic over the outlying track switch. A signal control leverSGL is employed to set up the controls for wayside signals governingtraflic over the track switch, and is operable to three positions,namely, west, stop and east, as indicated by the reference characters W,S and E respectively, and operates suitable contacts which are shown inthe conventional manner. A second control lever SML is operable to eachof two positions N and R for setting up controls for a switch machineemployed to position a track switch in either its normal or reverseoperated position.

The section of track corresponding to the portion of track diagram shownat the control office is illustrated at the field station, which sectionof track includes a track switch TS arranged to route trafiic to or froma diverging section of track which may be the entrance of a passingsiding and is operated by a switch machine SM which is in turncontrolled by a two-position polar relay WZ. Suitable wayside signalsES, WS and WSA are shown in the conventional manner as governing trafiicmovements over the track switch TS, and the trafiic direction isgoverned by selectively clearing the signals according to the energizedposition of a three-position polar relay SZ.

Various other relays at both the control ofiice and the field stationare shown in the conventional manner and it may be here mentioned thatthe relay WK at the control office is of the double winding typearranged so that one or the other of these windings is energizeddepending upon the position of the switch control lever SML and byrelatively opposite polarities, but these coils are so connected thatthe magnetism in the relay remains the same regardless of the polarityof energization and this energization is maintained during a change ofposition of the lever SML by the overlapping lever contact as shown. Therelay SK at the control ofiice is of the three-position polar type,while the relay WLP is of the two-position polar type or is arranged toretain its last operated position until changed by an energization ofthe opposite polarity. Other polar and neutral relays at both thecontrol office and the field station have their operatingcharacteristics designated by the base lines thereof, that is the relayshaving a heavy base line have slower operating characteristics thanother relays which are not indicated in this manner.

The relay P at the field station is illustrated as being of the typedisclosed in the prior patent of O. S. Field, Patent No. 1,969,065,dated August 7, 1934, and it may be here mentioned that this relay whenenergized operates an armature about a center pivot point in equallytimespaced oscillations to periodically and alternately open and closeelectrical circuits. It is however desired to be understood that thepresent system is not limited to the use of such a relay as otherarrangements may be substituted, such as two neutral relays having theirenergizing circuits interlocked to produce alternate operation.

In tracing circuits in the description of the operation of the presentsystem, and will be considered opposite extreme terminals of a source ofenergy at the control ofiice, and also of a similar source of energylocated at the typical field station, and (0) will be considered to be acenter tap or common potential for these energy sources. It is also tobe understood that the common line wire COM is connected to the centertap (c) of both the control office source of energy and the fieldstation source of energy.

In the accompanying drawing, the track switch TS is shown in its normalposition for routing trafiic straight through on the main track, and itwill first be considered in describing the operation of the system thatthe operator desires to reverse this switch for routing traffic upon thepassing siding. The switch control lever SML is then moved to position Rwhich reverses the polarity on the switch control relay WZ at the fieldstation over a circuit from (0), through the winding of relay WZ, wire6, back contact I of relay P, front contact 8 of track relay TR, frontcontact 9 of relay EM, front contact IU of relay WM, over the line wireL back contact I I of relay SZP, wires l2 and [3, contact M of the leverSML in its reverse position, wire l5, through the upper winding of relayWK to This circuit is effective to shift the contacts of the relay WZfrom the right hand position, as shown, to their left or dotted positionwhich is then out of correspondence with the contacts of relay WPthereby closing a circuit to energize the impulsing relay P from contactI6 of relay WP to the right wire l'l, contact l8 of relay WZ to theleft, wires l9 and 20, through the relay P to Current thus flowing inrelay P first flows through coil A and through contact 2| to the leftwhich shunts coil B thus attracting the armature to the right whichshunts coil A instead of coil B through contact 2|, and this actionobviously continues to produce an oscillation of the relay contacts.This operation of relay P then obviously opens and closes the energizingcircuit for the relays WZ and WK at equally spaced time intervals butthe relay WZ having slow releasing characteristics is not affected bythis pulsating energization, but the relay WK at the control officehaving faster operating characteristics periodically attracts andreleases its armature.

The relay TK at the control ofiice having slow releasing characteristicsis energized when relay WK is picked up over an obvious circuitcompleted by front contact 26, but is not dropped when the relay WKmomentarily drops. In a similar manner, the relay WKA is picked upduring the period in which the relay WK is deenergized over a circuitfrom back contact 22 of relay SZP, front contact 23 of relay TK, backcontact 24 of relay WK, through its operating windings to The relay WKAhaving slow releasing characteristics similar to the relay TK is notdropped when the relay WK is momentarily energized and consequently acircuit is closed at its front contact 25 to pick up the slow releasingrelay WKB in a similar manner but during the period in which the relayWK is energized. In this manner the oscillation of the relay P at thefield station is effective to periodically interrupt the switch controlcircuit which is effective at the control oifice to pick up the slowreleasing relays TK, WKA and WKB thereby closing a circuit to energizethe out-of-correspondence light COR over a circuit obvious from thedrawing. The indicating light COR may be a miniature lamp placed withinthe rotary control switch SML so as to be visible from the front of thecontrol panel.

During the time that the relay P is operating in the manner to indicatethis out-of-correspondence condition, contact 5| of relay WZ beingpositioned to the left is effective to operate the switch machine SMover the reverse control wire RC in a manner to move the track switch TSto its reverse position. The energizing polarity of relay WP which isconnected in the usual manner to repeat the position of the track switchTS is then reversed to operate its contacts into correspondence withrelay WZ or contact I6 of relay WP is operated to the left incorrespondence with contact l8 of relay WZ to the left. The energizingcircuit for relay P is then opened which stops the impulsing of thecontrol line circuit at contact 7 thereby dropping relays WKA and WKB atthe control ofiice and extinguishing the out-of-correspondence lightCOR. A neutral contact 38 is provided on the relay WP which is effectiveto energize the relay P in the same manner as the out-of-correspondencecontacts whenever some abnormal condition prevents the switch TS fromassuming its extreme locked position, and obviously the COR light willbe energized at the control office in the manner just described.

Considering now that the operator desires to allow a train movement fromthe main track eastward onto the diverging track, the signal controllever SGL is moved to its clear eastbound position E. A circuit is thencompleted which positions the contacts of the signal control relay S2 tothe left, and picks up the series relay SZP at the control office, whichcircuit may be traced from (0), front contact 28 of relay WP, wire 29,contact 30 of relay WP to the left, wire 3|, contact 32 of relay WZ tothe left, wire 33, through the windings of relay SZ, wire 34, frontcontact 35 of relay TR, line wire L through the upper winding of relaySZP, wire 36, through contact 31 of the signal control lever SGL to theright to The relay SZP picking up opens the circuit for the relay WK atback contact H, but a stick circuit is then effective to hold up therelay WK from (c) front contact 39 of relay TK, wire 40, front contact4| of relay SZP, wire [3, contact [4 of the switch control lever SML tothe right, wire I5, through the winding of relay W'K to It is obviousthat this signal control may have ''been set up at any time subsequentto the setswitch control had been executed. This is because thepreviously traced switch control circuit immediately operated the switchcontrol relay WZ out of correspondence with the relay WP thereby makingthe signal control circuit incomplete by the contact 32 of relay WZbeing out of correspondence with the contact 30 of relay WP.

The series relay SZP at the control office picking, up opens the switchcontrol circuit at back contact H and shifts the line wire L to includethe signal indicating relay SK at the control oflice. The controlcircuits for the relays WM and EM are not shown in the accompanyingdrawing, but it is understood that they are connected in theconventional manner to be selectively de-energized according to thedirection invwhich a clear signal indication is displayed. The circuitsfor effecting the clearing of the signal ES have been diagrammaticallyindicated by the dotted line 53 which extends to contact 44 of relay SZin its left hand position 'but it is to be understood that this. controlcircult for the signal ES will include local block signailing circuitswhich enable a clear signal indication to be displayed only whenwarranted by the condition of the associated track. Consequently as soonas the signal ES is clear in accordance with the position of the signalcontrol lever SGL, the relay EM is dropped thereby applying energy tothe switch control circuit of a polarity which positions the contacts ofthe relay SK to the right over a circuit from through the windings ofrelay SK, front contact ll of relay SZP, line wire L front contact H] ofrelay WM, through back contact 9 of relay EM to The signal indicatingrelay SK now having its contacts positioned to the right in accordancewith the clear signal ES at the field station energizes the east boundclear signal indicating means ESK on the control panel from contact 42of relay SK to the right, wire 45, through the signal indicating meansESK to The maner in which a west bound signal WS or WSA may be clearedfrom the control office is obvious from the drawing, or if the signallever SGL is placed to the clear west bound position W, an oppositepolarity is placed upon the line circuit over wire L which positions thecontacts of relay SZ to the right. This position of relay S2 is theneffective to clear either of the westbound signals according to theposition of the track switch TS and is determined by contact 41 of relayWP which selects either signal WS or WSA as indicated by the dottedlines. It is also obvious that when either signal WS or WSA is cleared,the relay WM drops to apply a polarity of energy to the switch controlline circuit or line wire L which positions the contacts of relay SK tothe left. With the contacts of relay SK to the left, either the signalindicating means WSK or WSAK is energized depending on the position ofcontact 48 of relay WLP. The

relay WLP is of the two-position polartype and is controlled by contact59 to repeat the position of the switch control lever SML, but itsposition may be changed only when the signal indicating relay SK isde-energized because its energizing circuit includes the de-energizedconof energization on the series or upper winding thereof, and it isevident then that the relay SZP is held up as long as a signal is clear,or in other words, during the existence of a clear signal, a movement ofthe signal control lever SGL will not drop the relay SZP to extinguishthe indication, but such indication will exist until either the relay EMor W'M picks up to drop the relay SK at the control office. If someabnormal condition causes an M relay (WM or EM) to drop which does notcorrespond to the transmitted signal control or the position of leverSGL, the position of the relay SK will not correspond to the position ofthe lever SGL, and consequently the energizatio-n of the lower windingof relay SZP will oppose the energization of the upper winding therebyeffecting the dropping of the relay SZP which in turn de-energizes relaySK to alw relay SZP to again pick up. This alternate oscillation of therelays SZP and SK will continue as long as the signal indication is outof correspondence with the signal control, and obviously, the signalindicating light (such as ESK) will be flashed, or alternately energizedand de-energized in synchrO-nism with the oscillation of relay SK toindicate this out-of-correspondence condition.

Having now described the way in which the track switch TS may becontrolled from the. control ofiice and the manner in which signalgoverning movements over this switch may be cleared, it will beconsidered that a train enters the section of track including the switchTS thereby dropping the relay TR which is: a track relay controlled bythe conventional track circuit. It is obvious that the dropping of relayTR opens both line wires L and L at contacts 8 and 35 respectivelythereby dropping relay SZ at the field station and relay WK at thecontrol office. The dropping of relay WK opens the energizing circuitfor the slow releasing relay TK at front contact 25, which relay TK thendrops to close a circuit for energizing the track circuit indicatingmeans OSIYfrom back contact 54 of relay WKA, wire 55, back contact 56 ofrelay TK, through the indicating means OSI to Itv will also be obviousthat both the east and west bound signals will be at stop when the trackrelay TR is dropped thereby causing both relays WM and EM to be pickedup which drops relay SK to extinguish the existing clear signalindication at contact 42. Relay SZP is also dropped in as much as itsupper winding is de-energized at contact 35 of relay TR and its lowerwinding at contact 52 of relay SK, but relay WK cannot be again pickedup with the track relay down because the line wire L is broken atcontact 8.

A railway centralized trafiic controlling system has thus been providedwhich permits the control of a distant track switch by selecting thepolarity of energization of a line circuitincluding one line wire and acommon wire, or, that is. a line wire which may be used as a commonpotential for the entire system. This line circuit is normallymaintained energized with this selected polarity from, an energy sourceat the control point,

distant switch location, the circuit is alternately opened and closedfor substantially equal periods of time until the switch has beenpositioned in accordance with the newly transmitted control. Thisinterrupted energization is efiective at the control ofiice to pick upand hold up certain slow releasing relays which then are effective toenergize indicating means to inform the operator that the switch is outof correspondence with the position of the switch control lever, butthese relays are again dropped when the impulsing is stopped by a properoperation of the switch to thereby extinguish the out-of-correspondenceindication.

The signal governing movements in either direction over the track switchmay be selectively cleared by applying either of two polarities ofenergy to a second line circuit which consists of a second line wire andthe previously mentioned common wire. This second line circuit isnormally de-energized to efiect the displaying of a stop signal for bothdirections, and includes a series relay at the control ofiice whichpicks up when a clear signal control is transmitted and shifts the firstline circuit from its control office energization to a signal indicatingrelay. This signal control line circuit also includes correspondencecontacts at the field station which requires the position of the trackswitch to conform with the position of the switch control relay beforethe selected signal control may be registered. When a clear signal isdisplayed, an indication is transmitted to the aforesaid signalindicating relay at the control ofiice by energizing the first mentionedline circuit at the field station with a polarity which is distinctiveof the particular traflic direction which the clear signal governs. Onefeature of the signal indicating means is that a movement of the signalcontrol lever from a clear to a stop position is not directly effectiveto extinguish the clear indication, but that the indication is onlyextinguished by removing the field station energy from the line circuit.Another feature of the signal indicating means is the provision againstincorrectly changing an existing indication of one clear signal toanother signal by a movement of the switch control lever.

A means for indicating the presence of a train on a track sectionassociated with the distant track switch has also been provided byopening both the previously mentioned line circuits at the field stationdue to the dropping of a conventionally arranged track relay, whichde-energization is eifective to drop a slow releasing relay at thecontrol ofiice thereby energizing a track section indicating means. Itwill be noticed that intermittently both of these line circuits aredeenergized during the transmission of an out-ofcorrespondence switchposition but such deenergized periods are arranged to exist for ashorter time than is effective to drop the aforesaid slow releasingrelay.

The above rather specific description of one form of the presentinvention is given solely by the way of example, and is not intended, inany manner whatsoever, in a limiting sense. It is also to be understoodthat various modifications, adaptations and alterations may be appliedto meet the requirements of practice, without in any manner departingfrom the spirit or scope of the present invention, except as limited bythe appended claims.

Having thus described my invention, what I claim is:--

1. In a railway traific controlling system, a control ofiice, a distanttrack switch and associated directional signals, two line circuitsconnecting the control OfilCB and the track switch and signals, atwo-position control relay associated with said track switch andselectively operable to either position according to the polarity ofenergy applied to the first of said line circuits, contact oscillatingmeans arranged to alternately open and close said first line circuitwhenever the position of said control relay is out of correspondencewith the position of said track switch, means at the control ofliceresponsive to the opening and closing of said first line circuit toindicate said out-of-correspondence condition, and means for selectivelyclearing said signals in either direction in accordance with thepolarity of energy applied to the other of said two line circuits onlywhen said two-position control relay is in a position corresponding tothe position of said track switch.

2. In a railway trafiic controlling system, a control office, a distantfield station, a first line circuit connecting the control office andthe field station, a track switch control means at the field stationpositioned according to the polarity of energy applied at the controloflice to said first line circuit, means for indicating at the controlofiice an out-of-correspondence condition between the track switch andsaid control means by alternately opening and closing said first linecircuit, a second line circuit connecting the control ofiice and thefield station, signal control means at the field station governed by theenergization of said second line circuit, and means for indicating aclear signal condition at the control office by energy applied at thefield station to said first line circuit.

3. In a railway traific controlling system, a control ofiice, a distantfield station, a first line circuit connecting the control office andthe field station, a track switch control means at the field stationpositioned according to the polarity of energy applied at the controloffice to said first line circuit, means for indicating at the controlofiice an out-of-correspondence condition between the track switch andsaid control means by alternately opening and closing said first linecircuit, a second line circuit connecting the control ofiice and thefield station, signal control means arranged to selectively cleartraffic signals in either direction according to the polarity ofenergization of said second line circuit, and means for indicating aclear signal condition at the control oifice by energy applied at thefield station to said first line circuit.

4. In a railway trarfic controlling system, a control office, a distantfield station, a first line circuit connecting the control office andthe field station, a track switch control means at the field stationpositioned according to the polarity of energy applied at the controloffice to said first line circuit, means for indicating at the controloflice an out-of-correspondence condition between the track switch andsaid control means by alternately opening and closing said first linecircuit, a second line circuit connecting the control ofiice and thefield station, signal control means arranged to selectively cleartraffic signals in either direction according to the polarity ofenergization of said second line circuit, and means for indicating thegoverning direction of a clear signal condition by the polarity ofenergy applied to said first line circuit.

5. In a railway trafllc controlling system, a h

control ofiice, a field station, a normally ener gized line circuitconnecting the control ofilce and the field station, means forcontrolling a track switch at said field. station according to the 5polarity of energization of said line circuit, an

oscillating contact means at said field station operable to impulse saidline circuit when the position of said track switch does not correspondto the polarity of said line circuit energization,

means at the control ofiice responsive to impulsing energization of saidline circuit, a second line circuit connecting the control ofiice andthe field station, means at the field station arranged to deenergizesaid normally energized line circuit and 'said second line circuit whena train occupies a particular track section, and means at the controlofiice distinctly responsive to the said de-energization of said linecircuits.

6. In combination, a control office, a field sta- 'tion, a first linecircuit connecting the control office and the field station, means forcontrolling a track switch at the field station by energizing said firstline circuit, a second line circuit connecting the control ofiice andthe field station,

r neans for clearing a signal at the field station by energizing saidsecond line circuit at the control oifice, a signal indicating means atsaid central ofiice, means for initially connecting said first linecircuit to said signal indicating means "at the control office only whensaid second line circuit is energized and thereby deenergizing saidfirst line circuit, and means for energizing said first line circuit atthe field station when said signal is clear.

7. In combination, a control oilice, a field station, a first linecircuit connecting the control office and the field station, means forcontrolling a track switch at the field station over said first linecircuit, a second line circuit connecting the ,control office and thefield station, means for clearing either of two signals at the fieldstation by selecting the polarity of energization of said second linecircuit at the control office, a signal indicating means at said controlofiice, means tor initially connecting said first line circuit to saidsignal indicating means at the control ofiice only when'said secondlinecircuit is energized,

and means for energizing said first line circuit at the field stationwith one polarity or another depending upon which of the two signals iscleared.

8. In combination, a control ofiice, a field sta-.

tion, a first line circuit connecting the control office' and the fieldstation, means for controlling :a track switch at the field stationoversaid first line circuit, a second line circuit connecting the controlofiice and the field station, means for clearing either of two signalsatthe field station by selecting the polarity of energization of saidsecond line circuit at the control office, means for connecting saidfirst line circuit to a signal indicating means at the control officewhen said second line circuit is energized, and means for energizingsaid first line circuit with a distinctive polarity' when'one of saidsignals is clear, and

means for de-energizing said first and said second line circuits toindicate at the control ofiice an occupied condition of a track sectionat the field station.

,21, 9. In combination, a track switch, a control lever for said trackswitch, a switch control relay, a switch control circuit arranged toposition said switch control relay in accordance with the position ofsaid switch control lever, an oscillat- 75 lingrelay arranged toperiodically open andclose said switch control circuit when the positionof said switch control relay is outof correspondence with the positionof saidtrack switch, a first slow releasing relay arranged to hold upduring the periodic opening and closing of said switch 5 controlcircuit, a second relay arranged to pick up during the periodic openingof said control circuit providing said first relay is picked up and tohold up during the periodic closing thereof, a third relay arranged topick up during the 10 periodic closing of said line-circuit providingsaid first and second relays are picked up and to hold up during theperiodic opening thereof, and an indicating "means energized when saidfirst, second and third relays are picked up. 15 5 10. In combination, atrack switch, a control lever for said track switch, a switch controlrelay, a switch control circuit arranged to position said switch controlrelay in accordance with the position of said switch control lever, anoscillat- 20 in;

ing relay arranged to periodically open and close said switch controlcircuit when the position. of said switch control relay is out ofcorrespondence with the position of said track switch, a first slowreleasing relay arranged to hold up during 25 the periodic opening andclosing of said switch control circuit, a second relay arranged to-pickup during the periodic opening of said control circuit providing saidfirst relay is picked up and i to hold up during the periodic closingthereof, 30,.

a third relay arranged to pick up during the periodic closing of saidline circuit providing said first and second relays arepicked up and toholdup during the periodic opening thereof, an indicating meansenergized when said first, second 35 i. and third relays are picked up,means for continuously opening said switch control circuit during thepresence or" a train on said track switch, and a second indicating meansresponsive to said continuous opening of said switch control circuit.11. In combination, a track switch, directional signals associated withthe track switch, a switch control relay, a control. circuit for saidswitch control relay, a signal control relay, a normally de-energizedcontrol circuit for said signal control relay, means for positioningsaid signal control relay by selecting the polarity of energization ofsaid signal control circuit, a relay arranged to 7 connect said switchcontrol circuit to a signal indicating relay when said signal controlcircuit is energized, and means for applying energy to said switchcontrol circuit of a polarity determined by the governing direction of aclear signal to thereby position said signal indicating means.

12. In combination; a control location; a distant traffic controllingdevice; a line circuit connecting the control location and the distanttrafficcontrolling device; a control lever at the control locationeffective to energize said line circuit with opposite polarities ofcurrent; a polarized relay at the trafiic controlling device, saidpolarized relay being included in said polarized line circuit and causedto assume opposite positions depending upon the polarity of the currentapplied to said line circuit by said control lever; indicationtransmitting means for at times opening andclosing said line circuitperiodically in accordance with said trafiic controlling device;indication receiving means at the control-location so constructed andincluded in said line circuit 7 g and associated with said control leverasto be responsive to the periodical opening and closing of said linecircuit by said indication transmitting means'but to be unafiected by areversal of the'polarity of said line circuit, whichreversal 757';

(a Ia indication relay having one winding or the other included in saidline circuit depending upon the position of said control lever tothereby respond to the open or closed condition of said line circuit butto be unresponsive to a change in the polarity of current in said linecircuit; an oscillating relay arranged to periodically open said linecircuit when the position of said polar relay is out of correspondencewith said track switch; other means for at times steadily opening saidline 'circuit; and indication means controlled by said double woundindication relay so as to give distinctive indications in accordancewith whether said indication control relay is steadily energized,steadily deenergized, or periodically de- -energized; whereby theoperation of said control lever does not efiect said indication means.

14. In combination, a track switch and signals for governing trafiicthereover, a control lever for governing said track switch, indicationmeans for indicating when said signals are cleared or at stop, a relaycapable of being positioned in accordance with said lever only whilesaid indication means indicates stop, and indicator means distinctivelycontrolled by said relay only when said indication means indicates thatsaid signals are cleared.

15. In a trafiic controlling system for railroads; a track switch andsignals for governing trafiic thereover; a switch machine for operatingsaid track switch; control relay means for governing the operation ofsaid switch machine; a control lever; a line circuit connecting saidcontrol lever and said control relay means, whereby the manipulation ofsaid control lever governs said ;";control relay means; signal controlrelay means energized whenever said signals are to indicate clear;indication means for indicating when said signals indicate clear, whenrendered effective; a relay picked up whenever said signal control linecircuit is energized; means opening said switch control line circuit andrendering effective said indication means when said relay is picked up;and means energizing said relay independently of said signal controlline circuit so long as said indication means indicates clear; wherebysaid switch control lever is rendered ineffective once a signal is clearuntil that signal indicates stop independently of said signal controllever.

16. In combination, a line circuit connecting two spaced locations;means for at times applying energy to said line circuit from one of saidlocations and at other times from the other of said locations; means atsaid other location for impressing any one of a plurality of distinctiveconditions on said line circuit, said conditions including a steadyenergization of one polarity or the other when energy is applied to saidline circuit from said other location, and said conditions including asteady energization, a steady deenergization, or an intermittentdeenergization when energy is applied to said line circuit from said onelocation; means at said other location for determining which particulardistinctive condition is to be impressed on said line circuit; and meansat said one location controlled in accordance with the distinctiveconditions impressed on said line circuit.

17. In combination, two spaced locations interconnected by two lineWires, a source of energy at one of said locations and provided with amidtap connected to one of said line wires, an indication relay havingtwo windings, control means for connecting either one terminal of saidsource to the other of said two line wires in series with one of saidwindings in one relationship or the other terminal of said source tosaid other of said two line wires in series with the other of saidwindings in an opposite relationship and said control means beingcapable of shifting from one terminal to the other without deenergizingsaid relay, a polar relay at the other of said locations for controllinga traflic device and being included in the line circuit formed by saidtwo line wires, means for at times opening the line circuit formed bysaid two line wires to thereby deenergize said indication relay, andother means controlled by said indication relay.

18. In combination; a line circuit connecting a control oflice and adistant traffic controlling device; a control lever at the control omcefor energizing said line circuit with positive or negative energy;transmitting means at said tratfic controlling device capable ofperiodically opening and closing said line circuit, when saidtransmitting means is energized; a polar relay included in series insaid line circuit for controlling said traffic controlling device, thecontacts of said polar relay being responsive to a change in thepolarity of the energy applied to said line circuit but beingunresponsive to said periodic opening and closing of said line circuitby said transmitting means; a neutral relay having windings; means soconnecting said windings of said neutral relay in said line circuit bysaid control lever that the reversal of the polarity of the energyapplied to said line circuit by said control lever maintains the samedirection of magnetic flux in said relay; whereby the contacts of saidrelay are unresponsive to a reversal of the polarity of the energyapplied by said control lever but are responsive to said periodicopening and closing of said line circuit by said transmitting means;indication means controlled by said neutral relay; and means at saidtrafiic controlling device for at times energizing said transmittingmeans in accordance with the condition of said traffic controllingdevice.

19. In combination; a line circuit connecting a control ofiice and adistant trafiic controlling device; a control lever at the controlofiice for energizing said line circuit with current of one polarity orthe other; transmitting means at said traffic controlling device capableof periodically opening and closing said line circuit, when saidtransmitting means is set into operation; a polar relay included inseries in said line circuit for controlling said traffic controllingdevice, the contacts of said polar relay being responsive to a change inthe polarity of energy applied to said line circuit but unresponsive tosaid periodical opening and closing of said line circuit by saidtransmitting means; a neutral relay; means for causing said neutralrelay to be picked up when ever steady current flows in said linecircuit and to remain picked up upon a reversal of the polarity ofcurrent in said line circuit by said control lever but to be droppedaway whenever said line circuit is periodically opened by saidtransmitting means or whenever said line circuit is steadilydeenergized; indication means controlled by said neutral relay andcapable of giving a distinctive indication in accordance with the steadyenergization, periodical opening, or steady deenergization of said linecircuit; means at said traffic controlling device for at times settingsaid transmitting means into operation in accordance with the conditionof said traffic controlling device; and means for at times steadilydeenergizing said line circuit in accordance with traffic conditions.

20. In combination; a line circuit connecting a control ofiice and adistant traffic controlling device; a control lever at the controloffice for energizing said line circuit with positive or negativeenergy; transmitting means at said traffic controlling device operableto periodically open and close said line circuit when said transmittingmeans is energized; a slow acting polarized relay included in series insaid line circuit for governing said traific controlling device, thecontacts of said polarized relay being responsive to a change in thepolarity of the energy applied to said line circuit but unresponsive tosaid periodic opening and closing of said line circuit by saidtransmitting means because of the slow acting characteristics of saidpolar relay; a neutral relay having two windings; means so connectingsaid two windings of said neutral relay in said line circuit by saidcontrol lever that the reversal of the polarity of the energy applied tosaid line circuit by said control lever maintains the same direction ofmagnetic flux in said neutral relay, whereby the contacts of saidneutral relay are unresponsive to a reversal of the polarity of theenergy applied by said control lever but are responsive to said periodicopening and closing of said line circuit by said transmitting means;indication means controlled by said neutral relay; and means at saidtraffic controlling device for at times energizing said transmittingmeans.

THOMAS J. JUDGE.

